Projection systems are widely used in training, sales, and business environments. Referring to FIG. 1, a projection system 100 includes a projector 102 positioned on a horizontal surface 104. The surface 104 is typically a desk or tabletop. An elevator 120 protrudes from the bottom sides of the projector 102 creating an angle 110 between the surface 104 and the projector 102. Only one elevator 120 is visible in FIG. 1 although a person of reasonable skill in the art should understand that a plurality of elevators 120 might be employed in the system 100. Likewise, a person of reasonable skill in the art should recognize that the projector 102 refers to any system capable of projecting any of a variety of still or moving images, e.g., projection televisions, multimedia projectors, computer displays, and the like.
The angle 110 varies depending on the position of the elevator 120. The elevator 120 tilts the projector 102's position relative to the surface 104 such that projected image 118 moves up or down on a projection surface 114, increasing or decreasing the angle 110. The projection surface 114 might be a wall, screen, or any other surface capable of displaying a projected image 118.
The projector 102 manipulates image signals 108 it receives from a personal computer 106. A person of reasonable skill in the art should recognize that the projector 102 might receive different types of image signals, e.g., digital or analog signals, from the personal computer 106. The image signals 108 represent still, partial, or full motion images of the type rendered by the personal computer 106.
The projector 102 casts the image signals 108 onto the projection surface 114. The resulting projected image 118 centers about a projection axis 116. An angle 112 exists between the projection axis 116 and the projection surface 114. The angle 112 changes responsive to changes in the angle 110.
The projected image 118 is substantially undistorted if the projection axis 116 is perpendicular to the projection surface 114. That is, the image 118 is undistorted if the angle 112 is 90 degrees. The projected image 118, however, distorts if the projection axis 116 is not perpendicular to the projection surface 114. This distortion is termed keystone distortion (or keystoning) because the image will appear wider at the top than at the bottom as shown in the jagged lined image 122.
The angle the projector 102 has relative to the surface 114 is therefore important in preventing the projected image from distorting. During set up, the user will typically rotate the projector 102 using a First Horizontal Last Vertical (FHLV) methodology. Referring to FIGS. 2A–B, a user horizontally rotates the projector 102 by rotating it about the substantially flat surface 104 as shown in FIG. 2A. The user then vertically adjusts the projector 102 by e.g., raising or lowering the elevators 120 as shown in FIG. 2B. The projector's vertical adjustment raise e.g., the front two edges of the projector above the surface 104 (FIG. 2B). The projector 102's electronics and optics correct the image using hardware and software that support FHLV such that the projected image 118 exhibits diminished keystone distortion. The projector 102 corrects the image responsive to e.g., a user's input. FHLV hardware and software, unfortunately, limit the keystone correction possible due to warping restrictions. And the optics are costly and prone to dust collecting often resulting in obscured projected images.
The projector 102 might include gauges 124 used to manually adjust the projected image 118 to eliminate or minimize keystone distortion. The manual adjustments tend to move the projected image 118 out of the projection surface 114. And the manual adjustments, unfortunately, are time consuming, cumbersome, and generally an unwelcome set up complication.
Accordingly, a need remains for a keystone correction system and method.